It seems to me to be more than just an accident of financial planning that the new Superman film was released in the States on July 4. The release of this film sets the crown on the past few years: years in which Hollywood has responded to wider cultural anxieties by making film after film after film about American strongmen wearing tights. That's a return, and also a retreat. America has decided, it seems, that it could do with a red cape as a comfort blanket.

I'm not being entirely facetious. Superheroes are a very important part of the American myth. The foundational playground question, Stephen King once wrote, was: "Who do you prefer: Superman or Batman?" Most of us would say: Batman. Batman is cool. Batman is dark. Batman has pointy ears. Superman, with his red pants outside his trews and his mild-mannered alter-ego, is the opposite of cool: the goody-two-shoes hilariously dismissed by a character in Frank Miller's graphic novel Batman: The Dark Knight Returns as "the big blue schoolboy".

But the two represent obverse sides of the same thing. The careers of both characters are rooted in orphanhood. Batman's response to being orphaned is an unceasing war of revenge; Superman's response to orphanhood, I think you could say, is to adopt. Having lost his own world, he adopts ours. Batman is mortal, human, vulnerable. He has no powers, and responds to a threatening world, and his own grief, with aggression and rage. Superman, by contrast, is all but omnipotent. He doesn't need to leap over tall buildings with a single bound. He can fly over them; or through them. The world is not so much a threat to him, as to itself. He is not an avenger, but a protector.

If you'll indulge me in the analogy, Batman is the role America finds itself playing in the world. Superman is what it would like to be. So it seems to me entirely understandable that, at a time of horrible uncertainty, Hollywood has chosen to bring him back to the centre of America's conversation with itself.

Superman represents a fantasy rooted in childhood, yet one that becomes ever more resonant as you pass into adulthood. Superman is the omnipotent father, rescuer, protector. A toy god. A catcher in the rye who can catch all the children; who can put a girdle round the earth and make time run backwards (in the first film, he does just this, bringing the dead victim of a catastrophe back to life); who is, literally, bulletproof.

Superman's myth of origin allies him with a character on this side of the Atlantic who has also returned after a long leave of absence. Like Superman, Dr Who is in exile, the last of his kind, a refugee from a vanished race and a destroyed world. At the centre of the appeal of both is the fulfilment of an infantile wish: that time does not run ineluctably forwards, and that we aren't on our own.

Superman is a live presence in the Flaming Lips' beautiful album The Soft Bulletin: "And though they were sad, they rescued every one. They lifted up the sun..." The overture to the album is called Waitin' for a Superman. "Tell everybody waiting for Superman," pleads the band's singer, Wayne Coyne, "that they should try to hold on best they can. He hasn't dropped them, forgot them, or anything. It's just too heavy for Superman to lift..."

unfortunately, some things are too heavy for Superman to lift. Myths like Superman tend to arise out of deep need - the more extravagant the fantasy of escape, the more there is to escape from. The early American superhero comics were the work of gauche, bullied, first-generation Jewish immigrant kids struggling between wars in depression-era America.

And Superman didn't come to the rescue of his creators, Joe Shuster and Jerry Siegel, who had the character stolen from them and spent most of their later lives all but destitute, before finally winning back their right to be identified with their greatest creation.

The progress of the film's actors, too, offers a grim rebuke to the myth. Superman didn't come to the rescue of Christopher Reeve, paralysed from the neck down after his riding accident. Superman didn't come to the rescue of Margot Kidder, the first Lois Lane, who struggled for years against madness.

Superman represents, as superheroes always have, a childlike bulwark against the adult realisation that some sorrows can't be comforted, that some vulnerable things can never be protected, and that there are things that are broken that can never be put back together again. But a fantasy he is. Things are bad down here. We are, in the words of the Flaming Lips, still waiting for a Superman.